Increasing efficiency of power generation plants is in progress in response to demands for reduction of carbon dioxide, resource conservation, and the like. Specifically, increasing temperature of working fluid of a gas turbine and a steam turbine, employing a combined cycle, and the like are actively in progress. Further, research and development of collection techniques of carbon dioxide are in progress.
FIG. 3 is a system diagram of a conventional gas turbine facility in which a part of carbon dioxide generated in a combustor is circulated as working fluid. As illustrated in FIG. 3, oxygen separated from an air separator (not illustrated) is regulated in flow rate by a flow rate regulating valve 310 and is supplied to a combustor 311. Fuel is regulated in flow rate by a flow rate regulating valve 312 and is supplied to the combustor 311. This fuel is, for example, hydrocarbon.
The fuel and oxygen react (combust) in the combustor 311. When the fuel combusts with oxygen, carbon dioxide and water vapor are generated as combustion gas. The flow rates of fuel and oxygen are regulated to be of a stoichiometric mixture ratio in a state that they are completely mixed.
The combustion gas generated in the combustor 311 is introduced into a turbine 313. The combustion gas which performed an expansion work in the turbine 313 passes through a heat exchanger 314 and then further through a heat exchanger 315. When passing through the heat exchanger 315, the water vapor condenses into water. The water passes through a pipe 316 and is discharged to the outside. Note that a generator 317 is coupled to the turbine 313.
Dry working gas (carbon dioxide) separated from water vapor is compressed by a compressor 318. A part of the compressed carbon dioxide is regulated in flow rate by a flow rate regulating valve 319 and is exhausted to the outside. The rest of the carbon dioxide is heated in the heat exchanger 314 and is supplied to the combustor 311.
Here, in the gas turbine facility, turbine load control is performed from a full speed no load (FSNL) to a rated value. Thus, the flow rate of working fluid introduced into the turbine 313 varies. The pressure of the working fluid in this gas turbine facility is at high pressure, and thus the volumetric flow rate of the working fluid in the compressor 318 is small. Accordingly, as the compressor 318, an axial compressor is not suitable, and a centrifugal compressor is used.
A part of the carbon dioxide supplied to the combustor 311 is introduced into a combustion zone together with the fuel and oxygen. The rest of the carbon dioxide is used to cool wall surfaces of the combustor 311 and dilute the combustion gas. Then, the carbon dioxide introduced into the combustor 311 is introduced into the turbine 313 together with the combustion gas.
In the above-described system, an amount of carbon dioxide equivalent to the amount of carbon dioxide generated by combusting fuel and oxygen in the combustor 311 is exhausted to the outside of the system. The carbon dioxide exhausted to the outside of the system is collected by, for example, a recovery apparatus. Further, for example, it is also possible to utilize the exhausted carbon dioxide for pushing out residual oil from an underground rock formation of an oil field. On the other hand, the carbon dioxide left in the system circulates through the system.
In the above-described conventional gas turbine facility, flame formed in the combustor 311 is affected by, for example, a jetting velocity of carbon dioxide jetted into the combustor 311 (hereinafter referred to as a combustor jetting velocity V).
This combustor jetting velocity V is defined by following equation (1).V=G×T×R×Z/(P×A)  (1)
Here, G is a volumetric flow rate of carbon dioxide flowing into the combustor 311, T is a temperature of carbon dioxide flowing into the combustor 311, R is a gas constant, and Z is a coefficient of compressibility. Further, P is a pressure of carbon dioxide flowing into the combustor 311, and A is a total opening area of an opening passed through by carbon dioxide which flowed into the combustor 311.
As described above, the flame is affected by the combustor jetting velocity V. Accordingly, when the turbine load control is performed in the gas turbine facility, for example, it is preferred to control this combustor jetting velocity V in an appropriate range so as to achieve stabilization of the flame.
However, in the centrifugal compressor used as the above-described compressor 318, for example, inlet guide vanes similar to that in the axial compressor is not provided, and thus it is difficult to perform flow rate control in a wide range. Accordingly, when the turbine load changes, it is difficult to control the combustor jetting velocity V in an appropriate range.